XII. Chemical Analysis of an Uncommon Species oJTuYjq- 

 LiTE. By Robert Kennedt, M. D., F. R. S., F. A. S., md 

 Fellow of the Royal College of Phyficians, Edinburgh. 



[^Read Jan. ii. 1802.] 



THE zeolite fubjedted to the following experiments, poflefles 

 fome of the diftinguifhing properties common to other 

 ftones of the fame clafs, but differs in certain refpedls from any 

 variety with which I am acquainted. I found it, more than 

 three years ago, in the bafaltic rock on which the Caftle of Edin- 

 burgh is built ; and it was inclofed within a mafs of prehnite. 



The colour of this zeolite is in fome parts nearly white, in 

 others greyifh white. It is compofed entirely of ftraight fibres, 

 arranged in bundles or maffes of different fizes, all the fibres of 

 each mafs converging towards a common point. The whole 

 fpecimen is an aggregate of thefe maffes, the bafes of which are 

 in contadl with the prehnite, and are impreffed with the form 

 of its furface, which is rounded, or botryoidal. The crofs frac- 

 ture prefents the irregular and ragged ends of the broken fi- 

 bres, termed xhc: hackly fradture by Mr Kirwan. 



Although the fliape and arrangement of the fibres appear 

 plainly to be the effedls of cryftallization, yet 1 have not been 

 able to trace a perfedlly regular, determinate form in any of them. 

 However, when the ftone is broken, fome of them can be readily 

 feparated longitudinally, in a pretty entire ftate, and feem in moft 



P p 2 inflances 



